Wells – Processes – Placing or shifting well part
Reexamination Certificate
1999-10-04
2002-11-05
Bagnell, David (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S127000, C166S332700, C166S334100
Reexamination Certificate
active
06474419
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a packer apparatus for use in cased wellbores, and more specifically relates to a packer apparatus which will equalize the pressure above and below a packer element after the packer has been set, so that the packer may be easily disengaged from the wellbore or repositioned for additional use.
The use of different types of packers in wellbores to sealingly engage the wellbore or a casing in the wellbore is well known. There are a number of different types of packers, and packers are utilized for a number of different purposes. One type of packer utilizes a packer element which is compressed so that it will expand into and sealingly engage casing in a wellbore. Such packers are utilized for treating, fracturing, producing, injecting and for other purposes, and typically can be set by applying tension or compression to the work string on which the packer is carried. The packer can be utilized to isolate a section of the wellbore which may be either above or below the packer, depending on the operation to be performed.
Once a particular operation, for example fracturing a formation, has been performed, it may be desirable to unset or release the packer and move it to another location in the wellbore and set the packer again to isolate another section of the wellbore. Generally, a pressure differential across the packer element will exist after an operation in the wellbore is performed. For example, when fracturing fluid pumped through a work string is communicated with the wellbore adjacent a formation, the pressure above the packer element, which will be located below the formation, will be higher than the pressure below the packer element after the operation is performed. In order to unset the packer, the pressure above and below the packer element which engages the casing must be equalized. Normally, in order to equalize the pressure, the formation must be allowed to flow. If, because of the nature of the operation performed or due to the position of the packer, the pressure below a packer is greater than the pressure above the packer, pressure in the wellbore above the packer may be increased by displacing a higher or lower density fluid into the wellbore above the packer or by pressurizing the area above the packer. Once the pressure is equalized, the work string can then be manipulated to unset the packer.
There are a number of difficulties associated with the present methods of isolating formations utilizing packers lowered into a wellbore on coiled tubing. One manner of isolating sections is to utilize opposing cup packers which are well known in the art. To isolate a particular section of a wellbore, such a system utilizes upper and lower cup packers that are energized simply by flowing through a port between the packers which causes expansion of the packers by creating a differential pressure at the cups. Pressure may be equalized before attempting to move the packer by flowing the well back up the tubing. There are some difficulties associated with such a method, including leak-off and compression, and safety concerns because of the gasified fluids communicated to the surface. It is also sometimes necessary to reverse-circulate fluids to reduce the differential pressure used to set the cup packers. There are environments, however, where it is difficult to reverse-circulate. Although some opposing cup tools have a bypass which will allow the pressure above and below the tools to equalize, the bypasses cannot handle environments wherein fluids have a high solids content.
Although such a system may work adequately, compression packers are more reliable and create less wear on the coiled tubing. Compression packers utilized on coiled tubing to isolate a section of a wellbore typically have a solid bottom such that communication with the wellbore through the lower end of the packer is not possible and the only way to equalize pressure and unset the packer is by flowing the well or by pressurizing the wellbore. This presents many of the same problems associated with a dual cup packer system. If the tools are moved when differential pressure exists, damage may occur and such operations can be time-consuming and costly. Thus there is a need for a packer apparatus which can be repeatedly set and unset and moved within the wellbore without the need for flowing or pressurizing the wellbore to unset the packer.
There is also a need for such a packer apparatus which can be actuated primarily by reciprocation, so it can be effectively utilized on coiled tubing.
SUMMARY OF THE INVENTION
The present invention relates to a packer used for isolating formation in a wellbore. The packer has an equalizing valve which allows differential pressure across the packer element to be equalized after the packer has been set so that the packer can be easily unset and moved within the wellbore even in high solids environments.
The packer comprises a housing adapted to be connected in a work string lowered into the wellbore. The housing defines a longitudinal opening therethrough. An expandable packer element is disposed about the housing for sealingly engaging the wellbore, or the casing in the wellbore, below a desired formation which intersects the wellbore. The equalizing valve is disposed in the housing and is movable between an open and a closed position. In the open position, flow is allowed through the longitudinal opening in the housing through a lower end thereof into the wellbore. In the closed position, the equalizing valve seals the longitudinal opening so that flow through the housing is prevented. The valve moves to its closed position as the packer is actuated to set the packer element to sealingly engage the casing.
When the packer element sealingly engages the casing and the valve is in its closed position, the portion of the wellbore above the packer element is isolated from the portion of the wellbore therebelow. Thus, fluid may be displaced into the work string and through a port defined in the work string into the wellbore above the packer to perform a desired operation on the formation. If desired, the formation can be produced. When an operation requiring that fluid be displaced into the wellbore is performed, a pressure differential is created such that the pressure above the packer element exceeds that below the packer element. Once the desired operation is performed, it may be desirable to release the packer and to move the packer within the wellbore to another location to complete other operations or to retrieve the packer from the well. To unset the packer, the pressure above and below the packer element must be equalized before the packer can be moved or the tool string may be damaged. With the present invention, pressure is equalized by moving the valve from its closed to its open position, thereby unsealing the longitudinal opening in the housing and allowing the portion of the wellbore above the packer element to communicate with the portion of the wellbore below the packer element which will equalize the pressure above and below the element.
The packer housing includes a packer mandrel having a drag sleeve disposed thereabout. The packer element is disposed about the packer mandrel above the drag sleeve. The equalizing valve comprises a generally tubular element that is connected to a lower end of the drag sleeve and extends upwardly into the longitudinal opening defined by the packer mandrel and the drag sleeve. Communication is prevented by lowering the packer mandrel relative to the drag sleeve which is held in place by the casing in the wellbore. The valve will move upwardly relative to the mandrel until it engages a reduced diameter portion of the mandrel which effectively seals the opening and prevents flow therethrough. When it is desired to equalize pressure, upward pull is applied to the mandrel to allow flow therethrough and automatically equalize the pressure above and below the packer element.
REFERENCES:
patent: 2301624 (1942-10-01), Holt
patent: 3306366 (1967-02-01), Muse
patent: 3433301 (1969-03-0
Maier Gary
Schmelzl Eric
Stromquist Marty L.
Halliburton Energy Service,s Inc.
Kent Robert A.
Rahhal Anthony L.
Wustenberg John W.
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